1.\" $NetBSD: pathconf.2,v 1.2 1995/02/27 12:35:22 cgd Exp $ 2.\" 3.\" Copyright (c) 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)pathconf.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt PATHCONF 2 38.Os BSD 4 39.Sh NAME 40.Nm fpathconf , 41.Nm pathconf 42.Nd get configurable pathname variables 43.Sh SYNOPSIS 44.Fd #include <unistd.h> 45.Ft long 46.Fo fpathconf 47.Fa "int fildes" 48.Fa "int name" 49.Fc 50.Ft long 51.Fo pathconf 52.Fa "const char *path" 53.Fa "int name" 54.Fc 55.Sh DESCRIPTION 56.Pp 57The 58.Fn pathconf 59and 60.Fn fpathconf 61functions provides a method for applications to determine the current 62value of a configurable system limit or option variable associated 63with a pathname or file descriptor. 64.Pp 65For 66.Nm pathconf , 67the 68.Fa path 69argument is the name of a file or directory. 70For 71.Nm fpathconf , 72the 73.Fa fildes 74argument is an open file descriptor. 75The 76.Fa name 77argument specifies the system variable to be queried. 78Symbolic constants for each name value are found in the include file 79.Li <unistd.h> . 80.Pp 81The available values are as follows: 82.Pp 83.Bl -tag -width "123456" 84.Pp 85.It Li _PC_LINK_MAX 86The maximum file link count. 87.It Li _PC_MAX_CANON 88The maximum number of bytes in terminal canonical input line. 89.It Li _PC_MAX_INPUT 90The minimum maximum number of bytes for which space is available in 91a terminal input queue. 92.It Li _PC_NAME_MAX 93The maximum number of bytes in a file name. 94.It Li _PC_PATH_MAX 95The maximum number of bytes in a pathname. 96.It Li _PC_PIPE_BUF 97The maximum number of bytes which will be written atomically to a pipe. 98.It Li _PC_CHOWN_RESTRICTED 99Return 1 if appropriate privileges are required for the 100.Xr chown 2 101system call, otherwise 0. 102.It Li _PC_NO_TRUNC 103Return 1 if file names longer than KERN_NAME_MAX are truncated. 104.It Li _PC_VDISABLE 105Returns the terminal character disabling value. 106.It Li _PC_FILESIZEBITS 107The minimum number of bits needed to represent, as a signed integer value, the maximum size of a regular file allowed in the specified directory. The max file size is 2^(_PC_FILESIZEBITS - 1). 108.It Li _PC_XATTR_SIZE_BITS 109Returns the number of bits used to store maximum extended 110attribute size in bytes. For example, if the maximum 111attribute size supported by a file system is 128K, the 112value returned will be 18. However a value 18 can mean 113that the maximum attribute size can be anywhere from 114(256KB - 1) to 128KB. As a special case, the resource 115fork can have much larger size, and some file system 116specific extended attributes can have smaller and preset 117size; for example, Finder Info is always 32 bytes. 118.It Li _PC_MIN_HOLE_SIZE 119If a file system supports the reporting of holes (see 120.Xr lseek 2 ) , 121.Fn pathconf 122and 123.Fn fpathconf 124return a positive number that represents the minimum hole size returned in 125bytes. 126The offsets of holes returned will be aligned to this same value. 127A special value of 1 is returned if the file system does not specify the minimum 128hole size but still reports holes. 129.El 130.Sh RETURN VALUES 131If the call to 132.Nm pathconf 133or 134.Nm fpathconf 135is not successful, \-1 is returned and 136.Va errno 137is set appropriately. 138Otherwise, if the variable is associated with functionality that does 139not have a limit in the system, \-1 is returned and 140.Va errno 141is not modified. 142Otherwise, the current variable value is returned. 143.Sh ERRORS 144If any of the following conditions occur, the 145.Nm pathconf 146and 147.Nm fpathconf 148functions shall return -1 and set 149.Va errno 150to the corresponding value. 151.Bl -tag -width ENAMETOOLONGAA 152.\" =========== 153.It Bq Er EINVAL 154The value of the 155.Fa name 156argument is invalid. 157.\" =========== 158.It Bq Er EINVAL 159The implementation does not support an association of the variable 160name with the associated file. 161.El 162.Pp 163.Fn pathconf 164will fail if: 165.Bl -tag -width ENAMETOOLONGAA 166.\" =========== 167.It Bq Er EACCES 168Search permission is denied for a component of the path prefix. 169.\" =========== 170.It Bq Er EIO 171An I/O error occurs while reading from or writing to the file system. 172.\" =========== 173.It Bq Er ELOOP 174Too many symbolic links are encountered in translating the pathname. 175This is taken to be indicative of a looping symbolic link. 176.\" =========== 177.It Bq Er ENAMETOOLONG 178A component of a pathname exceeded 255 characters, 179or an entire path name exceeded 1023 characters. 180.\" =========== 181.It Bq Er ENOENT 182The named file does not exist. 183.\" =========== 184.It Bq Er ENOTDIR 185A component of the path prefix is not a directory. 186.El 187.Pp 188.Bl -tag -width ENAMETOOLONGAA 189.Fn fpathconf 190will fail if: 191.\" =========== 192.It Bq Er EBADF 193.Fa fildes 194is not a valid open file descriptor. 195.\" =========== 196.It Bq Er EIO 197An I/O error occurs while reading from or writing to the file system. 198.El 199.Sh SEE ALSO 200.Xr sysctl 3 201.Sh HISTORY 202The 203.Nm pathconf 204and 205.Nm fpathconf 206functions first appeared in 4.4BSD. 207